The proposed research harnesses the opportunities provided by single molecule spectroscopy and micro/nano fabrication technologies to create an enabling tool for the systems biology research of neural stem cell. Its goal is to quickly map protein-protein interactions of the proteins, which may play a role in controlling the proliferation and differentiation for the neural stem cells. Its objective is to generate/identify all possible interacting partners for surface proteins of a neural stem cell and to confirm their functionalities in living cells. Its approach is to utilize single-phage-display to screen a cDNA library of neural stem cell for the isolation of the corresponding interaction partners. Single-phage-display (SPD) engages a unique combination of micro-fabrication, phage display and single molecule detection and characterization technology such as fluorescence correlation spectroscopy (FCS). The concept is based on 1) the compartmentalization of a library solution (by either micro-channels or micro-droplets) to a level that each compartment only hosts a single phage particle statistically; 2) the interrogation of binding status of the phage particle in each individual compartment by FCS and 3) the identification of the phage particle that binds to the target by phage display. To ensure the capability of identifying interaction partners "on demand", single phage display without FCS was also proposed as a backup approach. [unreadable] [unreadable]